As an example of a semiconductor device, a semiconductor power module including a semiconductor element for controlling electric power is known. It is known that, in a power conversion device configured using a semiconductor power module, noise is produced by the switching operation of the semiconductor element, the potential variations in a motor driven by the power conversion device, and the like. Since such noise leads to malfunctions of various electronic devices, a noise filter is inserted so as to suppress noise.
As one of the noise suppression means described above, there is a method of utilizing, as a noise filter, a capacitance produced between a semiconductor element and a heat dissipation conductor. Since the electrode joining a semiconductor element is generally connected to a heat dissipation conductor through a thin insulator, a capacitance exists between the semiconductor element and the heat dissipation conductor. This capacitance is utilized as a filter to control the path through which a noise current flows, thereby suppressing noise.
For example, Japanese Patent Laying-Open No. 2015-149883 (PTD 1) discloses a power conversion device configured to suppress noise by utilizing a capacitance produced between a semiconductor element and a heat dissipation conductor as a proximity bypass capacitor. Furthermore, this power conversion device includes a remote bypass capacitor that is longer in current path than the proximity bypass capacitor and greater in capacitance than the proximity bypass capacitor, thereby allowing suppression of noise in a large frequency region.